Coulomb’s law & electric fields worksheet with answers

Free printable Coulomb’s law & electric fields worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
++2 µC++2 µCr = 3 cm

Two point charges of +2 µC and +2 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = +2 µCr = 3 cm
F = N
2.Easy
−−4 µC++6 µCr = 6 cm

Two point charges of −4 µC and +6 µC are 6 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −4 µCq2 = +6 µCr = 6 cm
F = N
3.Medium
++8 µC++6 µCP10 cm

A charge of +8 µC and a charge of +6 µC are 10 cm apart. Point P lies on the line between them, 4 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = +6 µCr1 = 4 cmr2 = 6 cm
E = N/C
4.Medium
++4 µC−−5 µC−−10 µC5 cm + 5 cm

Three point charges lie on a straight line: +4 µC on the left, −10 µC on the right 10 cm away, and −5 µC between them, 5 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².

qL = +4 µCqR = −10 µCqM = −5 µCrL = 5 cmrR = 5 cm
F = N
5.Hard
8 cm10 cm+q1​ = +8 µC+q3​ = +6 µC+q2​ = +2 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 8 µC is 8 cm from it along one side and q₂ = 2 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 2 µCq3 = 6 µCr13 = 8 cmr23 = 10 cm
F = N
6.Hard
10 cm3 cm+q1​ = +6 µC+q3​ = +1 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 6 µC is 10 cm from it along one side and q₂ = 10 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 10 µCq3 = 1 µCr13 = 10 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 39.96 N
  2. 2. F = 59.93 N
  3. 3. E = 2.997 × 10⁷ N/C
  4. 4. F = 251.7 N
  5. 5. F = 68.28 N
  6. 6. F = 100 N

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